Siemens will be constructing the HVDC link for the Danish grid service provider Danish Energinet.dk and its Dutch counterpart TenneT TSO. In addition to enhancing power supply reliability in both countries, the COBRA cable will promote the integration of renewable energy sources into the power grid. Siemens will supply two HVDC converter stations at both sides of the DC power line, which will be routed as a subsea cable through the North Sea. The cable itself will be supplied by Italian company Prysmian, one of the world’s leading cable manufacturers. The link is scheduled to start commercial operation in early 2019 and has been designated as one of the European Commission’s projects of common interest to help create an integrated EU energy market.
“We are extremely pleased to drive forward the development of a high-performance, European interconnected power system together with Energinet.dk, TenneT and Prysmian” said Jan Mrosik, CEO of the Siemens Energy Management Division. “In fiscal 2015, Siemens commissioned HVDC Plus links with a total capacity of 4.9 gigawatts throughout Europe. With the COBRA order we will bring projects with a further 4.6 gigawatts online over the next few years, thus making a significant contribution to integration of a European power grid.”
TenneT CEO Mel Kroon added that Siemens and Prysmian are excellent partners to undertake the realization of the project which will help to promote competition in the Northwest European energy market. This will in turn benefit consumers in both countries and increase security of supply. It will also enable the Netherlands to import more renewable electricity, generated mainly by Danish wind farms.
Two 700 MW converter stations are included within the project for a DC voltage of ±320 Kilovolt (kV). One of the stations will be constructed at Eemhaven in Holland while the other will be sited in Endrup in Denmark. A 325 kilometer DC power cable will link the two stations. Energinet.dk will be responsible for erecting the building at Endrup to house the Siemens converter equipment at that station while Siemens will supply the turnkey converter station in Eemshaven. The order also includes system design and the supply, installation and commissioning of all components.
The two converter stations will use HVDC Plus voltage-sourced converters in a modular multilevel converter arrangement (VSC-MMC) that convert AC to DC and DC back to AC on the other side of the link. In contrast to line-commutated converter technology, the HVDC Plus system works with power transistors that can also be switched off (IGBT), enabling the commutation processes in the power converter to run independently of the grid voltage. The very fast control and protective intervention capabilities of the power converters provides a high level of stability in the transmission system, which primarily serves to reduce grid faults and disturbances in the three-phase AC network. This significantly increases supply reliability for utility companies and power customers. HVDC is moreover the only solution that provides low-loss and economical transmission of electricity for cable-connected high-voltage links over distances of more than 80 kilometers.
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